rules_rust VS cargo-chef

The same reason Bazel builds avoid using Cargo when building Rust software, so I'll describe why Bazel would do this:

- Bazel wants to cache remote resources, like each respective crate's source files.

- Bazel then wants to build each crate in a sandbox, and cache the build artifacts

This is an established practice, and Nix wants to drive the build for the same reasons.

See:

- https://github.com/bazelbuild/rules_rust

- https://github.com/google/cargo-raze

To answer your question, I don't know if Soong or Bazel can reuse the files produced by an incremental Rust compilation. I tried searching the rules_rust repository and found some discussions, but nothing that clearly told me "Yes, this is supported".

Bazel doesn't allow targeting a lot of platforms (especially embedded) from Rust, even when the Rust ecosystem supports these targets. Something is off with its design if new work needs to be done for every platform that's already available behind an interface that's as consistent as what rustc gives.

What is supported needs to be inferred from this file, as far as I can tell: https://github.com/bazelbuild/rules_rust/blob/main/rust/plat...

You might be overjoyed to learn that you can use a build tool that forces you to manually write out the dependencies between each file.

I am using rules_rust and have the VS Code Bazel plugin installed, but I am still not getting autocomplete.

Other than that, the performance of both for builds should be determined exactly by the organization of code into separate crates and the rustc invocations. Bazel generally encourages smaller crates, but that's very subtle. There is at least 1 case I can think of where rustc is overfit to cargo, in a way that is not easily replicable by bazel, which is the metadata/rlib pipelining https://github.com/bazelbuild/rules_rust/issues/228

Rust integrates pretty seamlessly into Bazel projects via rules_rust (https://github.com/bazelbuild/rules_rust). The existing rules even allow for c calling rust and rust calling c. Example: https://github.com/bazelbuild/rules_rust/blob/main/examples/...

With any compiled language you can use the compiler and vendor your dependencies instead of using the language's conventional package manager. For example, nothing prevents skipping Cargo and building Rust directly with rustc the way Bazel does.

https://github.com/bazelbuild/rules_rust

CI time. Do you want to micromanage your own docker images for all your CI? Great! If not, yes you do. In fact, you want to manage a docker image to build a docker image to use for CI. Use cargo-chef to prepare a build image with your dependencies pre-built if you want to do fine-grained build/test pipelines. Oh also, there's no jUnit test report generation, that was killed off today. (YES, SORRY, I'm still salty.)

Have you looked at cargo-chef? It supposedly speeds up compilation times if you're using Docker.

A tool already exists for this called Cargo-chef, and it works extremely well.

At work I've use Dockerfile and cargo-chef to improve build times. You can also look into buildkit cache mounts, but this approach is rarely super effective on hosted CI because they start from scratch on most runs. In the context of Rust specifically you may also see the target directory reflect unbounded data growth if it's reused over and over across revisions. because cargo by default won't expire older intermediate artifacts. Cargo-sweep can help with that but I wouldn't pursue this in a CI effort. This will affect both "native" builds and buildkit cache mounts if you're persisting the target directory.

We create an empty Rust binary with cargo new, this is a simple way to get Docker layer caching to work. For a more robust solution, you may want to check out cargo-chef.

If this ends up being a cleaner/easier way to having to workaround super expensive rebuilds for Rust given cache + deps compared to this https://github.com/LukeMathWalker/cargo-chef , reading this thread will have been a huge win for me (and hopefully others).

Whether introducing Bazel is easier/worth it, subjective I guess.

I did a talk (slides here) about this a few years ago, it took a bit of work to get the build caching working with cargo. As others have pointed out, there is now cargo chef to solve this problem so you probably don't have to deal with the issues I saw, but I thought it still might be helpful context.

I'm curious if you've tried out cargo-chef, I've had some decent improvements with it but I wonder how it stacks up to the sccache approach (don't have the time to try it out myself right now).

for CI have you tried to use buildkit persistent runners with caching + https://github.com/LukeMathWalker/cargo-chef ?

If you're deploying Rust with Docker I can tell you that cargo-chef is invaluable. With zero work it caches the dependency fetch and compilation steps. Most of the time the ens Docker deploy is closer to an incremental compile than full.